diff --git a/benchmark/util/util-format.js b/benchmark/util/util-format.js
@@ -0,0 +1,41 @@
+// Copyright (c) 2014, Ben Noordhuis <info@bnoordhuis.nl>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+'use strict';
+
+var common = require('../common.js');
+var format = require('util').format;
+
+var bench = common.createBenchmark(main, {});
+
+function main(conf) {
+  var fmts = [];
+
+  for (var i = 0; i < 26; i += 1) {
+    var k = i, fmt = '';
+    do {
+      fmt += '%' + String.fromCharCode(97 + k);
+      k = (k + 1) % 26;
+    } while (k != i);
+    fmts.push(fmt);
+  }
+
+  bench.start();
+
+  for (var i = 0; i < 1e5; i += 1)
+    for (var k = 0; k < fmts.length; k += 1)
+      format(fmts[k]);
+
+  bench.end(1e5);
+}
diff --git a/lib/_linklist.js b/lib/_linklist.js
@@ -24,6 +24,7 @@
 function init(list) {
   list._idleNext = list;
   list._idlePrev = list;
+  return list;
 }
 exports.init = init;
 
@@ -57,6 +58,7 @@ function remove(item) {
 
   item._idleNext = null;
   item._idlePrev = null;
+  return item;
 }
 exports.remove = remove;
 
@@ -68,6 +70,7 @@ function append(list, item) {
   list._idleNext._idlePrev = item;
   item._idlePrev = list;
   list._idleNext = item;
+  return item;
 }
 exports.append = append;
 

diff --git a/lib/sprintf.js b/lib/sprintf.js
@@ -0,0 +1,187 @@
+// Copyright (c) 2014, Ben Noordhuis <info@bnoordhuis.nl>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+'use strict';
+
+var L = require('_linklist');
+var inspect = require('util').inspect;
+var quickeval = process.binding('contextify').quickeval;
+
+function LRU(maxsize) {
+  this.dict = Object.create(null);
+  this.list = L.init({});
+  this.size = 0;
+  this.maxsize = maxsize;
+}
+
+LRU.prototype.find = function(key) {
+  var val = this.dict[key];
+
+  // Move to front of the list unless it's already the first node.
+  if (val && val !== L.peek(this.list))
+    L.append(this.list, L.remove(val));
+
+  return val;
+};
+
+LRU.prototype.insert = function(key, val) {
+  while (this.size >= this.maxsize) {
+    delete this.dict[L.shift(this.list).key];
+    this.size -= 1;
+  }
+
+  var val = L.append(this.list, {key: key});
+  this.dict[key] = val;
+  this.size += 1;
+
+  return val;
+};
+
+function format(fmt /*, ... */) {
+  return vsprintf(fmt, arguments, compat);
+}
+
+function sprintf(fmt /*, ... */) {
+  return vsprintf(fmt, arguments, extended);
+}
+
+function vsprintf(fmt, argv, compile) {
+  if (typeof(fmt) !== 'string') {
+    if (compile === compat)
+      return concat(argv);
+    fmt = '' + fmt;
+  }
+
+  var lru = compile.lru;
+  var cached = lru.find(fmt);
+
+  if (cached === undefined) {
+    cached = lru.insert(fmt);
+    cached.fun = compile(fmt);
+  }
+
+  return cached.fun.apply(null, argv);
+}
+
+function concat(argv) {
+  var argc = argv.length;
+  var objects = new Array(argc);
+
+  for (var i = 0; i < argc; i += 1)
+    objects[i] = inspect(argv[i]);
+
+  return objects.join(' ');
+}
+
+// util.format() compatibility mode.
+function compat(fmt) {
+  var index = 0;
+  var argc = 0;
+  var body = '';
+
+  for (;;) {
+    var start = index;
+    index = fmt.indexOf('%', index);
+    var end = index === -1 ? fmt.length : index;
+
+    if (start !== end) {
+      body += ' s += "' + untaint(fmt.slice(start, end)) + '";';
+    }
+
+    if (index === -1)
+      break;
+
+    index += 1;
+
+    var c = fmt[index];
+    switch (c) {
+      case 'd':
+        // %d is really %f; it coerces the argument to a number
+        // before turning it into a string.
+        body += ' s += argc > ' + (argc + 1) + ' ? +a' + argc + ' : "%d";';
+        argc += 1;
+        index += 1;
+        continue;
+
+      case 'j':
+        body += ' if (argc > ' + (argc + 1) + ')';
+        body += ' try { s += JSON.stringify(a' + argc + '); }';
+        body += ' catch (e) { s += "[Circular]"; }';
+        body += ' else s += "%j";';
+        argc += 1;
+        index += 1;
+        continue;
+
+      case 's':
+        body += ' s += argc > ' + (argc + 1) + ' ? a' + argc + ' : "%s";';
+        argc += 1;
+        index += 1;
+        continue;
+
+      case '"':
+        c = '\\"';
+        // Fall through.
+
+      default:
+        body += ' s += "' + c + '";';
+        index += 1;
+        continue;
+    }
+  }
+
+  // The dummy argument lets format() and sprintf() call the formatter
+  // with .apply() without having to unshift the format argument first.
+  var source = 'return function(dummy';
+
+  for (var i = 0; i < argc; i += 1)
+    source += ', a' + i;
+
+  source += ') { var argc = arguments.length, s = "";' + body;
+  source += ' for (var i = ' + argc + ' + 1; i < arguments.length; i += 1) {';
+  source += ' var arg = arguments[i];';
+  source += ' if (arg === null || typeof(arg) !== "object") s += " " + arg;';
+  source += ' else s += " " + inspect(arg);';
+  source += ' }';
+  source += ' return s;';
+  source += ' };';
+
+  return Function('inspect', source)(inspect);
+}
+
+function untaint(s) {
+  return s.replace(/[\\"]|[^\x20-\x7F]/g, function(c) {
+    switch (c) {
+      case '\t': return '\\t';
+      case '\n': return '\\n';
+      case '\f': return '\\f';
+      case '\r': return '\\r';
+      case '"': return '\\"';
+      case '\\': return '\\\\';
+    }
+    return '\\u' + ('0000' + c.charCodeAt(0).toString(16)).slice(-4);
+  });
+}
+
+compat.lru = new LRU(64);
+
+function extended(fmt) {
+  throw Error('unimplemented');
+}
+
+extended.lru = new LRU(64);
+
+// Hidden export for lib/util.js
+Object.defineProperty(sprintf, '_format', {value: format});
+
+module.exports = sprintf;
diff --git a/lib/util.js b/lib/util.js
@@ -21,45 +21,13 @@
 
 'use strict';
 
-var formatRegExp = /%[sdj%]/g;
-exports.format = function(f) {
-  if (!isString(f)) {
-    var objects = [];
-    for (var i = 0; i < arguments.length; i++) {
-      objects.push(inspect(arguments[i]));
-    }
-    return objects.join(' ');
-  }
-
-  var i = 1;
-  var args = arguments;
-  var len = args.length;
-  var str = String(f).replace(formatRegExp, function(x) {
-    if (x === '%%') return '%';
-    if (i >= len) return x;
-    switch (x) {
-      case '%s': return String(args[i++]);
-      case '%d': return Number(args[i++]);
-      case '%j':
-        try {
-          return JSON.stringify(args[i++]);
-        } catch (_) {
-          return '[Circular]';
-        }
-      default:
-        return x;
-    }
-  });
-  for (var x = args[i]; i < len; x = args[++i]) {
-    if (isNull(x) || !isObject(x)) {
-      str += ' ' + x;
-    } else {
-      str += ' ' + inspect(x);
-    }
-  }
-  return str;
-};
+var formatter;
+exports.format = function() {
+  if (!formatter)
+    formatter = require('sprintf')._format;
 
+  return formatter.apply(null, arguments);
+};
 
 // Mark that a method should not be used.
 // Returns a modified function which warns once by default.

diff --git a/node.gyp b/node.gyp
@@ -54,6 +54,7 @@
       'lib/_stream_duplex.js',
       'lib/_stream_transform.js',
       'lib/_stream_passthrough.js',
+      'lib/sprintf.js',
       'lib/string_decoder.js',
       'lib/sys.js',
       'lib/timers.js',